This continued investigation covers several aspects of mitochondrial biogenesis. Foremost is a complete characterization of the products of mitochondrial protein synthesis. These products include those found in association with the three enzyme complexes, cytochrome oxidase, ATPase and succinate cytochrome c reductase. There is reason to believe that some polypeptides function in more than one complex. We are also investigating the mechanism and order of assembly of the various parts of these enzyme complexes. Part of the same project includes an analysis of a large number of mutants that we have isolated that lack activity for one or more of the same 3 enzyme complexes.